I never put it together, but this is the same thing as what's now commonly called a multitool[0], and indeed the modern version evolved from a device specifically designed to cut casts without harming the flesh beneath[1]. Extremely versatile and easy to use for amateurs like me.
Yeah it took me a minute to realize this was from 98. When they were talking about the fien tool being a sander that you could get saw blades for, I was thinking....wait, I thought the fien tool was just a multitool. Anyway multitools are great! I use them all the time.
Should add (1998) to the title. Oscillating multi tools are now common place with DIYers since battery technology improved in the mid 2000s.
They were originally invented in the 1960s to remove plaster casts.